Protective cover for a plasticising cylinder

ABSTRACT

A protective cover for a plasticising cylinder of a shaping machinehas an elongate internal space which is enclosed by at least one wall and in which the plasticising cylinder can be arranged. A terminal box for heating strips arranged on the plasticising cylinder projects into the internal space, and one of the walls of the protective cover has an opening which is closed by an openable cover member. In the opened condition, the opening allows access to the terminal box or the interior of the terminal box.

BACKGROUND OF THE INVENTION

The present invention concerns a protective cover for a plasticising cylinder of a shaping machine having the features of the classifying portion of claim 1, a plasticising unit having such a protective cover and a shaping machine having such a plasticising unit.

DE 37 42 403 C1 discloses a protective cover in which a plug bar covers the end of a protective cover in the region beneath the plasticising cylinder.

Protective covers are known in which a terminal box is externally mounted to the protective cover.

SUMMARY OF THE INVENTION

The object of the invention is to provide a protective cover of a more compact structure, in which simple and rapid change of the plasticising unit is possible, as well as to provide a plasticising unit having such a protective cover and a shaping machine having such a plasticising unit.

That object is attained by a protective cover having the features of claim 1, a plasticising unit having such a protective cover and a shaping machine having such a plasticising unit. Advantageous embodiments of the invention are defined in the appendant claims.

The at least one wall can be of various different configurations (in isolation or as any combination), for example:

in the form of a single wall of curved shape, enclosing an internal space of at least about 90° to about 200°,

in the form of two straight walls in an L-configuration,

in the form of three straight walls in a U-configuration.

The shaping machine can be for example an injection moulding machine.

The invention affords a series of advantages:

it involves a very compact structure,

the terminal box remains easily accessible from the exterior for service operations,

freely hanging cables are no longer required on the entire plasticising unit whereby handling is markedly easier when changing the plasticising unit,

the cabling of the heating strips to the terminal box can be of a fixed nature. When changing the plasticising unit therefore there is no need for separation as between the heating strips and the terminal box.

a low number of plugs in the terminal box is achieved by the combination of a plurality of heating strip cables or heating strips on a plug.

the integration of the terminal box provides that only one interface is necessary in respect of various screw diameters and length/diameter ratios of the plasticising units. That permits simple and rapid change of a plasticising unit and the same cables can be used with different plasticising units, which permits standardisation of the cable lengths.

integration of the terminal box on the plasticising unit makes it possible to standardise the interface between a main switch cabinet of the shaping machine and the plasticising unit.

It is particularly preferably provided that the terminal box has a side which faces towards the plasticising cylinder in the mounted condition and which extends in the longitudinal direction of the internal space and is of a concave configuration. In that way the terminal box can so-to-speak fit snuggly to the cylindrical contour of the plasticising cylinder.

According to the invention there is at least one terminal box per plasticising unit, but there can also be a plurality of terminal boxes. The arrangement is preferably implemented on a lateral wall of the protective cover or a lateral portion of the at least one wall, but an arrangement at the top side or underside of the plasticising unit is also possible.

The ratio between the spacing of a lateral wall of the protective cover from the central axis of the plasticising cylinder and the external radius of the plasticising cylinder is in a range of about equal to 3 to about 1.1 (preferably from about equal to 2.5 to about 1.4) and is preferably less than or equal to 1.6.

It can also be provided that a control and/or power electronic system for the heating strips is arranged in the internal space in the protective cover, preferably in the terminal box. That permits decentral control and/or power supply for regulation of the heating strips. That decentralisation affords more space in the main switch cabinet of the shaping machine.

It is quite particularly preferably provided that the openable cover member is in the form of a cover member of the terminal box, wherein preferably the cover member of the terminal box adjoins flush the wall having the opening so that the terminal box is arranged completely in the internal space except for the cover member. In this embodiment the terminal box fits into the protective cover of the plasticising unit in the optimum fashion. As the terminal box does not protrude from the protective cover there are no pinch locations between the nozzle protection and the terminal box. As a result the means for protection from outspraying can be of a closely fitting configuration, which further enhances operator safety.

It can be provided that the interface plugs of the terminal box are so arranged that the plugging directions extend parallel to that wall of the protective cover that has the opening.

Preferably the interface plugs are adapted to be pluggable.

The integration of the terminal box on the heated plasticising cylinder, in particular with the snugly fitting structure, can require thermal uncoupling of the terminal box from the heating strips. That can be effected in various ways (individually or in any combination):

-   -   Reduction in the heat transfer by radiation by means of:         -   fitting beam protection plates between the terminal box and             the plasticising cylinder,         -   using beam protective films on the terminal box,         -   using insulating mats on the terminal box, and         -   insulating the plasticising cylinder.     -   Reduction in the heat transfer by conduction by using thermal         insulating elements in the mechanical connection of the terminal         box to the plasticising cylinder.     -   Reduction in the heat transfer by conduction by arranging a         defined air gap between the plasticising cylinder and the         terminal box.     -   Using a cooling device:         -   active cooling (preferably controlled) of the terminal box             by water or air cooling,         -   cooling ribs arranged on the terminal box,         -   using the chimney effect occurring through a gap between the             plasticising cylinder and the terminal box (cooling action             due to natural convection).

It can be provided that the plasticising unit has a display means and/or interface for an operator, for example:

displaying status information on a display (for example defective heating strips, currently prevailing temperatures and temperature distributions, currently prevailing switching state, remaining service life of the installed heating strips),

integrated user interface on the plasticising unit (for example the option of presetting the temperature or temperatures directly at the plasticising unit),

integrated interface on the plasticising unit to an external user interface (for example wirelessly or wired for a mobile or stationary device).

It is preferably provided that a cable run connecting the terminal box to the heating strips is arranged above the plasticising cylinder. If temperature-resistant cable is used the cable run can be arranged without an additional cable protection beneath the protective cover of the plasticising cylinder. Arranging the cable run above the plasticising cylinder affords advantages in terms of accessibility upon mounting or when replacing a defective heating strip. Alternatively the cable run can also be arranged laterally of the plasticising cylinder or inclinedly above the plasticising cylinder.

It is preferably provided that a nozzle heating strip and associated temperature sensor are connected to the terminal box by way of a plug connection. That provides that the nozzle heating strip can be very quickly changed.

The terminal box can have at least one information interface for the connection (for example plugging connection) of a sensor or data bus.

The plug which is closest to the filling opening of the plasticising cylinder ideally involves a defined spacing A with the same outside diameter of the plasticising cylinder and with a given structural size of the plasticising unit. The magnitude of the spacing A however can be freely selected.

Preferably the plugs are arranged protected so that they are not damaged when setting up the plasticising unit by means of an adjusting leg of the plasticising unit and a plasticising cylinder support.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is described with reference to the Figures in which:

FIG. 1 shows an isometric view of a plasticising unit according to the invention,

FIG. 2 shows a view of the end of the plasticising unit,

FIG. 3 shows a further view of the end of the plasticising unit,

FIG. 4 shows a side view of the plasticising unit,

FIG. 5 shows a protective cover according to the invention with opened cover member, and

FIGS. 6a-6c show isometric views from below on to the protective cover.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a portion of a plasticising unit of a shaping machine according to the invention, which otherwise corresponds to the state of the art. It is possible to see a protective cover 1 having two lateral walls 3 a, 3 b and an upper wall 3 c in a U-shaped configuration. The protective cover 1 is open downwardly. It is possible to see the plasticising cylinder 2 which is arranged in the internal space 4 in the protective cover 1 and on which heating strips 6 are arranged. The protective cover 1 has an opening 8 (see FIG. 5) which is closed in FIG. 1 by a cover member 7. In the illustrated embodiment the cover member 7 is in the form of a cover member of the terminal box 5 and adjoins the wall 3 a of the protective cover 1 in flush relationship. After removal of the screws (here six) which can be seen the content of the terminal box 5 is accessible from the exterior without further parts of the protective cover 1 having to be dismantled. The cover member 7 can naturally be openable in any fashion. In operation the plasticising cylinder 2 is supported on the underlying surface by way of a plasticising cylinder support 10. After the plasticising unit has been dismantled it can be supported preferably at least in a three-point support configuration by way of the plasticising cylinder support 10 and a further support 11 (which has for example at least two support points).

FIG. 2 shows that in this embodiment the terminal box 5 has a side which is towards the plasticising cylinder 2 and which extends in the longitudinal direction of the internal space 4 and is concave. The ratio between the spacing Y of a lateral wall 3 a, 3 b of the protective cover 1 from the central axis of the plasticising cylinder 2 and the external radius R of the plasticising cylinder 2 is in a range of Y/R approximately equal to 3 to about 1.1—preferably (Y/R) approximately equal to 2.5 to about 1.4—and is preferably less than or equal to 1.6 (see FIG. 3).

FIG. 4 shows a wide view of the plasticising unit shown in the preceding Figures, with a spacing A being illustrated. This involves the spacing A between a filling opening of the plasticising cylinder 2 and that plug which is closest to the filling opening of the plasticising cylinder 2. Ideally, with the same outside diameter of the plasticising cylinder 2 and a given structural size of the plasticising unit, it involves a defined spacing A. The magnitude of the spacing A however can be freely selected.

FIGS. 6a to 6c show views into the empty protective cover 1, that is to say without the plasticising cylinder 2 arranged in the internal space, but with the terminal box 5 being shown.

LIST OF REFERENCES

-   1 protective cover -   2 plasticising cylinder -   3 a, 3 b, 3 c walls of the protective cover -   4 internal space in the protective cover -   5 terminal box -   6 heating strip -   7 cover member of the protective cover -   8 opening in the protective cover -   9 side of the terminal box that is towards the plasticising cylinder -   10 plasticising cylinder support -   11 further support 

1. A protective cover for a plasticising cylinder of a shaping machine, having an elongate internal space which is enclosed by at least one wall and in which the plasticising cylinder can be arranged, wherein a terminal box for heating strips arranged on the plasticising cylinder projects into the internal space and one of the walls of the protective cover has an opening which is closed by an openable cover member and which in the opened condition allows access to the terminal box or the interior of the terminal box.
 2. A protective cover according to claim 1, wherein the terminal box has a side which faces towards the plasticising cylinder in the mounted condition and which extends in the longitudinal direction of the internal space and is of a concave configuration.
 3. A protective cover according to claim 2, wherein the ratio between the spacing of a lateral wall of the protective cover or a lateral portion of the at least one wall from the central axis of the plasticising cylinder and the external radius of the plasticising cylinder is in a range of (Y/R) approximately equal to 3 to about 1.1—preferably (Y/R) approximately equal to 2.5 to about 1.4—and is preferably less than or equal to 1.6.
 4. A protective cover according to claim 1, wherein a control and/or power electronic means for the heating strips is arranged in the internal space of the protective cover, preferably in the terminal box.
 5. A protective cover according to claim 1, wherein the openable cover member is in the form of a cover member of the terminal box.
 6. A protective cover according to claim 5, wherein the cover member of the terminal box adjoins in flush relationship the wall having the opening so that the terminal box is arranged completely in the internal space except for the cover member.
 7. A protective cover according to claim 1, wherein interface plugs of the terminal box are so arranged that the plugging directions extend parallel to that wall of the protective cover, that has the opening.
 8. A protective cover according to claim 1, wherein the opening is arranged at a lateral wall or a lateral portion of the at least one wall of the protective cover.
 9. A protective cover according to claim 1, wherein there is provided a cooling device for the terminal box.
 10. A plasticising unit for a shaping machine having a protective cover according to claim 1 and a plasticising cylinder in the internal space of the protective cover.
 11. A plasticising unit according to claim 10, wherein a cable run connecting the terminal box to the heating strips is arranged above the plasticising cylinder.
 12. A plasticising unit according to claim 1, wherein a nozzle heating strip and an associated temperature sensor are connected to the terminal box by way of a plug connection.
 13. A plasticising unit according to claim 1, wherein the terminal box has at least one information interface for the connection of a sensor or a data bus.
 14. A plasticising unit according to claim 1, wherein the terminal box is thermally insulated or uncoupled from the heating strips and the plasticising cylinder.
 15. A plasticising unit according to claim 1, wherein the plasticising unit has a plasticising cylinder support and a further support.
 16. A plasticising unit according to claim 1, wherein the plasticising unit has a display means and/or interface for an operator.
 17. A shaping machine, in particular an injection moulding machine, having a plasticising unit according to claim
 1. 